1. Field of the Invention
The present invention relates generally to a decoding system, and particularly to a decoding system capable of high speed decoding suitable for use in parity checking in digital information data transmission or recording with high reliability.
2. Description of the Prior Art
In transmission or recording and reproducing of digital information data, in order to prevent erroneous transmission or recording/reproducing of digital signal, a data sequence is blocked into blocked data of a predetermined length, and coding is performed for each blocked data. When a reliability and error characteristic of the transmission line or recording medium is not sufficient, there is a need to correct compound error wherein random error and burst error may exist together. Then, by randomizing the burst error into random error by means of interleaving, the random errors are corrected. When the object of error correction is only the random errors, or the compound errors, higher error correction capability for random errors contribute to higher reliability of digital information data. A product code has a characteristic the decoding the component code is easy with respect to its correction capability, and is good in harmonizing with the interleaving for correction of the compound error. Therefore the product code is being used more often for error correction in the system of transmission or recording of digital information data. In the code comprised of two or more component codes such as the product code, however, it is necessary that decodings of the component codes of the code must organically cooperate. For instance, in decoding of a product code constituted by two component codes, such repeated operation becomes necessary that after decoding a first component code, decoding a second component code is carried out by utilizing the result of the first decoding, and when necessary, decoding the first component code is repeated. Accordingly, in the decoding of the product code, though decoding of code of respective component codes are relatively simple, processing of the organic cooperation of the decoded results is complicated, and a general practical process has not yet been available in the prior art. The situation is the same for the case of a decoding process for the product code of two codes with a minimum distance 2 and a minimum distance t, which is a class of the product code. In transmission or recording of the digital information data, a high speed of processing is required for error correction, and hence, a method of high speed decoding of the product code becomes necessary.